Operating System & Its Concept

Definition:

An Operating System is a program which acts as an interface between the user and the computer hardware. The Purpose of an Operating system is to provide an environment in which a user may execute programs. The main aim of an Operating system

Is to make the computer system convenient to use. A secondary goal is to use the computer hardware in an efficient manner.

Functions of Operating System:

The following functions are performed by the system:

• Job sequencing, scheduling and traffic controller operation.
• Input/Output programming.
• Protecting itself from the user, protecting the user from other users.
• Secondary storage management.
• Error handling.

Important function of an operating system is to protect the user from unauthorized access of his files or data. Secondary storage management is a task performed by an operating system in conjunction with the use of disks, tapes and other secondary storage for the users programs and data.

An operating system must respond to errors. When an error occurs, operating system

Must take appropriate actions.

Multiprogramming:

The most important aspect of job scheduling is the ability to multiprogramming.

Offline operation buffering and spooling for overlapped I/O have their limitations.

Multiprogramming is the attempt to increase CPU Utilization by always having something for the CPU to execute.

Time sharing:

Time sharing systems are the result of trying to provide interactive use of a computer system at a reasonable cost.  A time shared Operating system allows many users to simultaneously share the computer. Since each action or command in a time –shared system tend to be short, only a little CPU time is needed for each user.

Distributed System:

At present in computer systems is to distribute computation among several physical processors. There are basically two schemes for building such systems. In a tightly coupled system the processors share memory and a clock.

In these multiprocessor systems, communication usually takes place through memory.

In a loosely packed system, the processors do not share memory or a clock.

Instead each processor has its own local memory. These systems are usually referred to as Distributed systems.

The Processor in a distributed system may vary in size and function. They may include small microprocessors, workstations, mini computers and large general purpose computer systems.These processors are referred to by a number of different

Names such as sites, nodes, computers and so on. depending on the context in which they are mentioned. We mainly use the term site, in order to emphasize the physical distribution of these systems.

There are four major reasons for building distributed systems namely resource sharing, computation speed up, reliabillty and communication.

Real – Time Systems:

A real time system is often used as control device in a dedicated application.  Sensors bring data to the computer. The computer must analyze the data and possibly   adjust controls to modify the sensor inputs. Systems which control scientific experiments, medical computer systems, industrial control systems and some display systems are real time constraints.